Nowadays, various blade shapes are proposed in order to achieve a low-noise and high-efficient air blower. In general, in order to achieve the low noise and the high efficiency of a fan, it is required to suppress fluctuation in pressure acting on the blades and reduce frictional loss between air streams by reducing turbulence of the air streams to be generated around the blades.
For example, in Patent Literature 1, there is disclosed a propeller fan in which aside surface of a boss having a plurality of blades mounted thereon is formed into a conical shape. In this propeller fan, as a radial cross-sectional shape of each of the blades, an outer side of a radial midpoint thereof has a concave curved line with respect to a windward side, and the outer side of the radial midpoint has a convex curved line with respect to the windward side. With such a configuration, a leakage vortex at a blade tip is stabilized to cause a smooth radial inflow in a high load region so that a static pressure is enhanced.